This invention relates in general to devices for supporting workpieces, and in particular to a workpiece support device that may be used for supporting a workpiece held by a fixture during a machining operation.
In many machining operations, the workpiece to be machined is held in place by a fixture. One common type of fixture includes an elevated horizontal frame having a plurality of clamps mounted around the perimeter of the frame. The workpiece is laid on top of the frame and clamped in place. A machining operation, such as cutting, milling or drilling, is performed on the top of the workpiece.
A problem with using this type of fixture is that the center portion of the workpiece is unsupported during the machining operation. As a result, the workpiece may be deflected downward from the force of the machining operation applied to the top of the workpiece. Such deflection may reduce the rate of production, make it difficult to maintaining close tolerances, and increase tool wear.
To address this problem, it is known to position a workpiece support device below the workpiece. A typical workpiece support device includes a body and an upwardly extendable support post having a rest portion on its upper end. The support post is extended upward until the bottom of the workpiece rests on the rest portion of the post. The support post is then locked in position by a locking sleeve or other device. The support post offers resistance to any downward force caused by the machining operation.
However, the locked support post of the typical workpiece support device does not apply upward pressure on the workpiece during the machining operation. This is a disadvantage, because some vibration and chatter of the workpiece may occur during machining, making the machining more difficult. Another disadvantage is that the locking sleeve may become contaminated with dirt, scrap material, or other contaminants after a period of use, which may cause the locking sleeve to lose its ability to function properly.
This invention relates to a workpiece support device which includes a body having a base portion adapted for mounting on a surface. The workpiece support device also includes a support member mounted on the body so as to be extendable outward relative to the body and away from the base portion, and retractable inward relative to the body and toward the base portion. The support member has an outer end adapted for supporting a workpiece, and it has an inner end. The workpiece support device also includes a cam member having a camming surface. The cam member is mounted on the body so as to be movable in first and second directions. The movement of the cam member in the first direction causes the camming surface to drivingly engage the inner end of the support member and force the support member to extend outward relative to the body. The movement of the cam member in the second direction allows the support member to retract inward relative to the body. The workpiece support device also includes an actuator which when turned on forces the cam member in the first direction, thereby forcing the support member to extend outward relative to the body.
In a preferred embodiment, the workpiece support device includes first and second cam members each having a camming surface. The cam members are mounted on the body so as to be movable between first and second positions relative to one another. The movement of the cam members between the first position and the second position causes the camming surfaces to cooperate to drivingly engage the inner end of the support member and force the support member to extend outward relative to the body. The movement of the cam members between the second position and the first position allows the support member to retract inward relative to the body. The workpiece support device includes at least one actuator which when turned on forces the cam members to move between the first position and the second position, thereby forcing the support member to extend outward relative to the body.